Hi Folks,
Looking for your expertise.
The problem: Random Misfires on cylinders 1,3,5 - Confirmed with Scanner
The Jeep: 2012 JKU 6-Speed, 108K miles
How long: I've been trying to fix this: 9 months
It's hard to feel the misfire when under throttle, but you can hear and feel the slight misfire trembles when at idle.
What I've tried so far:
- New Spark Plugs: (2 set's - 6 NKG & 6 Champion) Properly Gapped
- New Coils: MSD
- New O2 Sensors (all 4 - both sides)
- New Crankshaft Position Sensor
- New MAP Sensor
- All new Rocker Arms and Lifters on that bank (Cyl 1,3,5)
- New Camshaft Position Sensor
- New Injector on Cyl 5 = No change still misfiring
- New upper and lower o-rings for injectors
- New upper and lower o-rings for Lower and Upper Manifolds
Tests Completed:
- Leakdown Test Showed Normal
- Rotated Coils - No Change
- Rotated Plugs - No Change
- Camshafts inspection - no flat spots found
Additional Modifications Possibly Affecting Performance:
Mishimoto Oil Catch Can
Banks CAI
Odyssey Battery
Additional Fixes Completed on Motor:
- New Oil Pressure Sensor
Friends,
Please help. I love my jeep, and I want to drive it to 300k miles and drop in a Hemi and keep driving it.
(Wave),
Matt
Ok... The shop I work at swapped all the parts listed above AND the ECU and ALL Catalytic Converters...
Diagnostic steps include all of the above PLUS Smoke Testing the entire system from the throttle body and the tail pipe and Live Data (all PID's reporting) from our dealer level scan tool...
Bank 2's O2 Sensor was dutifully swapping between High and Low (Rich and Lean) readings and the Cylinder 2,4 and 6 Fuel Injectors are supplying fuel in 2000ms sips...
The Bank 1 O2 Sensor, however... Was stuck Low (lean) and at times reporting erroneous voltages... Like there is no way the mix could be so lean and the truck stay running erroneous... and of course... The injectors are pouring fuel in 8000ms dumps...
One would certainly think there is a huge vacuum leak somewhere and the System is heroically attempting to compensate by pouring gas on the mess...
But, all the new Intake/valve cover/PCV, etc. gaskets and a successful smoke test says nope... The only air in here is the known quantity that has passed through the MAF sensor...
So..
The thing was finally handed to our Lead Mechanic... Who is allowed to indulge in flights of whimsy and call it Troubleshooting... He even gets to fire the parts cannon from time to time...
While the rest of us have our time managed in 15 minute increments and all diagnostics and subsequent parts request must be peer reviewed and approved by a Manager...
But I digress ...
One of the things he tried was swapping fuel injector rails... The entire rail... From 1,3 and 5 to 2,4 and 6 and vice versa...
Low and behold...
The problem followed the injectors... So he pulls 3 new injectors and installs them in Cylinders 2,4, and 6....
The thing idles like new...
Now... I'm of the opinion that replacing the injectors also replaced some leaky o-rings that we couldnt see smoking due to them being completely under the intake manifold... But they're saying it was somehow the injectors themselves...
I tested the resistance of each replaced injector and they were all right in spec at 1.2ohms...
So what do I know...
But, replacing the injectors on the entire bank is what solved the problem... So I wanted to share that with everyone who is trying to get their own Pentastar powered abomination back on the road and isn't paid to do it...
Sorry for the long winded reply... But thank you for the opportunity to vent!
Roam8
Wherever I May...